Typically, street manholes are collection points for various sewer conduits converging on the manhole to disgorge their contents into a main line located at the bottom of the manhole. The manholes can be of many shapes and sizes, but typically are round in cross-section and have an opening at the top sufficient to enable a person to enter and do the appropriate service that may be required. The manhole frequently serves as a junction point where different sewer lines are joined to merge into a common discharge conduit in a manner, for example, as described in my U.S. Pat. No. 5,553,973.
The feed-in of discharge fluids from adjacent areas frequently enter a manhole at a higher level than the bottom located sewer line. The feed-in pipe then projects a small distance into the manhole to deliver a stream of discharge liquid into the middle of the manhole. Entry into the manhole then is impeded by this extended stream. Manhole drops have, therefore, been devised to provide a channel alongside the wall of the manhole for the sewer feed that comes in from the side. Such conventional manhole drop has an inlet pipe that extends into the manhole to a T shaped pipe as illustrated in FIG. 1 herein. one end of the T is plugged and the downwardly directed portion is coupled to a pipe that channels the side feed liquid down to the sewer line.
Typically the inside drop system has to be matched to the incoming feed line with a comparable pipe size. Since each feed pipe material has different measurement system and attachment system there would have to be an equal number of fittings or custom parts would have to be made up of sheet material. For smaller feed pipes a frequent solution involved the use of an inside drop pipe that is relatively large in cross-section and this is matched to the incoming feed line by simply cutting a hole into the drop pipe. This, of course meant that the entire drop pipe has to be removed to allow an inspection and cleaning of the incoming side feed line.
One problem with the conventional system of FIG. 1 is that it does not permit easy inspection of the feed line or of the drop itself. To see the feed line requires removal of the plug and the inside part of the drop is not visually accessible from above. These problems are eliminated with a drop system in accordance with the invention.